Security Camera System

ABSTRACT

A security camera system for safeguarding a designated area includes at least one camera for encoding and transmitting streaming video of the designated area, and a video receiver for receiving, decoding and analyzing the streaming video for relevant motion, such as movement indicative of the presence of a person. Upon detecting a motion event, the video receiver triggers an alert condition, which results in storing each video steam into memory. Each camera is provided with a PIR detector circuit for measuring infrared radiation within the designated area, the video steam and IR data being transmitted to the receiver via analog communication means to reduce implementation costs. To minimize the risk of false trigger events, the receiver monitors both pixel changes in the streaming video signals as well as measured IR radiation levels within the designated area that fall within the traditional thermal energy range of human body heat.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.15/345,307, filed Nov. 7, 2016 which claims the benefit of U.S.Provisional Application No. 62/251,945, filed Nov. 6, 2015.

FIELD OF THE INVENTION

The present invention relates generally to security camera systems and,more particularly, to security camera systems which are designed todetect the presence of relevant movement within a designatedenvironment.

BACKGROUND OF THE INVENTION

Security camera systems, also referred to herein simply as securitysystems, are well known in the art and are widely used, in bothresidential and business settings, to monitor and safeguard a designatedenvironment from intruders. One well-known type of security systemincludes at least one video surveillance camera that is connected to acommon digital recording device, such as a digital video recorder (DVR)or network video recorder (NVR), by a cable or other conventionalcommunication path. In use, each camera continuously compiles video ofthe monitored area and processes the video for transmission to thecommon video recording device. The common recording device, in turn,receives the encoded video signal compiled from each camera and decodesthe signal into a corresponding digital video stream.

The two principal types of video surveillance cameras that aretraditionally utilized in security systems are analog cameras anddigital cameras, which are also commonly known in the art as InternetProtocol (IP) cameras. Analog and digital cameras differ primarily inthat analog cameras process the compiled video signal to be transmittedto the common recording device in analog form, whereas digital camerasprocess the compiled video signal to be transmitted to the commonrecording device in digital form. As a consequence, it has been foundthat the two aforementioned types of video cameras differ principally incost, with analog cameras being generally less expensive than digitalcameras.

Commonly, security camera systems of the type as described above aredesigned to detect any relevant movement within the monitoredenvironment, such as the presence of an individual. Upon detecting suchmovement within the area under surveillance, the system is designed toinitiate a predefined response, such as the commencement of videorecording and/or activation of an alert signal. In this manner, securitycamera systems serve as effective tools in safeguarding a monitored areafrom unauthorized intruders.

Motion detection technology is often used to detect the presence of anindividual within the monitored environment. The detection of motionwithin the designated area is commonly achieved by examining pixelchanges in the compiled digital video streams. Specifically, a centralcontroller in the common recording device is programmed to measure pixelchanges in each digital video stream. Any detected pixel change thatexceeds a predefined threshold is considered a motion detection eventand, as such, causes the recording device to undertake the previouslydetermined motion detection response.

Although well-known and widely used in the art, security systems thatrely solely on pixel changes to detect relevant movement within themonitored environment have been found to suffer a notable shortcomingwith respect to accuracy. Specifically, it has been found thatmonitoring pixel changes in video streams frequently results inrelatively inconsequential movement triggering a motion detection event.Examples of irrelevant action which may induce a motion detection eventinclude, inter alia, (i) variances in light within the monitoredenvironment (e.g., resulting from lights being turned on/off, sunlightchanges and the like), (ii) movement of animals, insects, dust or othersmall elements within the monitored environment, and (iii) movement ofelements in the background (e.g., rain, wind-induced movement of trees,shrubs or swings) or immediately outside of the monitored environment(e.g., a moving car or rain seen through a window within the designatedarea). As can be appreciated, this detection of inconsequential movementwithin the monitored environment often results in unnecessary recordingsand alerts, which is highly undesirable.

In view thereof, it has become increasingly common for security systemsto monitor infrared radiation variances within the designatedenvironment, rather than monitor pixel changes in a digital video feed,in order to detect relevant movement within the area under surveillance(e.g., the presence of a person). For instance, it is known in the artfor security systems to equip a digital Internet Protocol (IP) camerawith a pyroelectric infrared radial (PIR) sensor circuit.

In use, the PIR sensor circuit measures infrared light that radiatesfrom objects in its field of view (e.g., thermal energy produced from aperson) in relation to the remainder of the monitored environment. Thedigital output signal from the PIR sensor circuit is then combined withthe streaming video signal during signal processing prior totransmission to the common recording device. The recording device thenanalyzes the infrared radiation signal component of the mixed signal. Ifany thermal energy variance is detected that can be attributed to, interalia, the standard body temperature range, the recording deviceinitiates the predefined motion detection response. In this manner, aneffective method for detecting a notable motion event within themonitored environment can be achieved.

As can be appreciated, the use of PIR sensors in security camera systemsto detect relevant movement within a monitored environment has beenfound to suffer from a couple notable shortcomings.

As a first shortcoming, PIR sensors are traditionally used with digitalcamera systems due to the processing capabilities of the signalprocessor responsible for combining and conditioning the digital PIRoutput signal with the digital video stream. However, as referencedbriefly above, digital cameras have been found to be relativelyexpensive in nature, largely due to the cost associated with theadvanced signal processor as well as the signal communication channelscommonly used in conjunction therewith (e.g. Ethernet cables).

As a second shortcoming, security camera systems which rely solely uponthe detection of infrared radiation within a defined thermal energyrange to initiate a trigger event have been found to be experiencereliability issues. Specifically, it has been found that unforeseenvariances in infrared radiation within the monitored environment canoften be attributed to conditions other than relevant movement (e.g.,the presence of people) and, as such, can induce false trigger events.Examples of non-human action which may induce a variance in infraredradiation within the designated temperature range include, inter alia,(i) rapid changes in sunlight radiation within the field of view, (ii)intense thermal energy changes caused by equipment within the monitoredenvironment (e.g., a burner), and (iii) sun, lightning or other brightlight reflecting off highly reflective surfaces (e.g., glass or a pool)toward the PIR sensor.

BRIEF SUMMARY OF THE INVENTION

It is an object of the invention to provide a new and improved securitycamera system for monitoring a designated environment.

It is another object of the present invention to provide a securitycamera system as described above that monitors the designatedenvironment using one or more continuous video streams.

It is yet another object of the present invention to provide a securitycamera system as described above that records the one or more continuousvideo streams upon detecting relevant movement within the designatedenvironment.

It is still another object of the present invention to provide asecurity camera system as described above that detects relevant movementwithin the designated environment with reliable accuracy.

It is yet still another object of the present invention to provide asecurity camera system as described above that is simple to use, readilyscalable in size, and inexpensive to implement.

Accordingly, as one feature of the present invention, there is provideda security camera system for monitoring a designated area for relevantmovement, the security system comprising (a) an analog videotransmitter, comprising, (i) an image capture device for producing astreaming digital video signal of the designated area, (ii) a PIRdetector circuit for measuring infrared radiation within the designatedarea, the PIR detector circuit producing a digital infrared radiationsignal that indicates relevant movement within the designated area basedon measured infrared radiation, and (iii) a signal processor forprocessing the digital video and infrared radiation signals together toyield a mixed analog signal, the signal processor transmitting the mixedanalog signal, and (b) a video receiver adapted to receive and decodethe mixed analog signal transmitted from the analog video transmitterinto a corresponding decoded digital signal, the video receiveranalyzing the decoded digital signal and triggering an alert conditionwhen the decoded digital signal indicates relevant movement within thedesignated area.

As another feature of the present invention, there is provided asecurity camera system for monitoring a designated area for relevantmovement, the security system comprising (a) a video transmitter,comprising, (i) an image capture device for producing a streamingdigital video signal of the designated area, (ii) a PIR detector circuitfor measuring infrared radiation within the designated area, the PIRdetector circuit producing a digital infrared radiation signal thatindicates relevant movement within the designated area based on measuredinfrared radiation, and (iii) a signal processor for processing thedigital video and infrared radiation signals together to yield a mixedsignal, the signal processor transmitting the mixed signal, and (b) avideo receiver adapted to receive and decode the mixed signaltransmitted from the video transmitter into a corresponding decodeddigital signal with multiple image frames, each image frame comprising aplurality of pixels, the video receiver detecting a number of pixelchanges between successive image frames in the decoded digital signal,(c) wherein the video receiver analyzes the decoded digital signal andtriggers an alert condition only when both the amount of measuredinfrared radiation and the number of detected pixel changes in thedecoded digital signal indicates relevant movement within the designatedarea.

Various other features and advantages will appear from the descriptionto follow. In the description, reference is made to the accompanyingdrawings which form a part thereof, and in which is shown by way ofillustration, an embodiment for practicing the invention. The embodimentwill be described in sufficient detail to enable those skilled in theart to practice the invention, and it is to be understood that otherembodiments may be utilized and that structural changes may be madewithout departing from the scope of the invention. The followingdetailed description is therefore, not to be taken in a limiting sense,and the scope of the present invention is best defined by the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings wherein like reference numerals represent like parts:

FIG. 1 is a simplified block representation of a security camera systemconstructed according to the teachings of the present invention, thesystem being shown with a simplified representation of person presentwithin a monitored environment;

FIG. 2 is a sample signal waveform of the mixed analog signaltransmitted by the camera shown in FIG. 1;

FIGS. 3(a) and 3(b) are front perspective and partially exploded sideviews, respectively, of one implementation of the camera shown in FIG.1; and

FIGS. 4(a)-(c) are a series of sample frames of the analog video streamproduced by the camera shown in FIG. 1, the sample video frames beinguseful in illustrating how security camera system detects and determinesa relevant motion event, wherein a portion of each sample frame in FIGS.4(b) and 4(c) is shown enlarged and exploded therefrom as an inset.

DETAILED DESCRIPTION OF THE INVENTION Security Camera System 11

Referring now to FIG. 1, there is shown a security camera systemconstructed in accordance with the teachings of the present invention,the security camera system being identified generally by referencenumeral 11. As will be explained further in detail below, securitycamera system 11 is designed to provide video surveillance of aparticular environment. As a primary feature of the present invention,system 11 is able to detect relevant movement within the monitoredenvironment (e.g., the presence of an individual) with great accuracyand at minimal cost to implement.

Security camera system 11 comprises at least one video transmitter, orcamera, 13 that is connected to a common video receiver, or recorder, 15by an appropriate communication channel 17. For simplicity purposesonly, system 11 is represented herein as comprising a single camera 13.However, it is to be understood that a plurality of cameras 13 could beconnected to common receiver 15 via corresponding communication channels17 without departing from the spirit of the present invention. In thiscapacity, surveillance could be achieved over a larger environmentand/or with greater overall effectiveness.

In use, each camera 13 is designed to continuously compile video of themonitored environment. The video signal is then transmitted via channel17 to video receiver 15 for analysis. If receiver 15 determines that arelevant motion event has taken place within the monitored environment,receiver 15 initiates a predefined alert response, such as commencingrecording of the video feed into a data storage device and/or activatingan alert signal.

As will be explained in greater detail below, system 11 is provided withtwo novel design features, each of which offers notable advantages overconventional security camera systems. Specifically, system 11 isdesigned to (i) utilize both infrared (IR) radiation-based motiondetection technology and pixel-based motion detection technology todetermine relevant movement within the monitored environment, therebyminimizing the frequency of false alert triggers and improving overallaccuracy, and (ii) operate as an analog system, with the temperaturedetection signal and the video signal compiled by camera 13 beingprocessed into a mixed analog signal that is transmitted to receiver 15via analog-based communication channel 17, thereby offering considerablecost savings to implement.

As seen in FIG. 1, each camera 13 comprises an optical system, or imagecapture device, 19 that produces a digital video signal S_(V), a PIRdetector circuit 21 that produces a digital IR radiation signal S_(IR),and an image signal processor, or ISP, 23 that processes the digitalvideo signal S_(V) and digital IR radiation signal S_(IR) together toyield a combined, or mixed, analog signal S_(A). As referenced brieflyabove, incorporating IR radiation detection technology into an analogsecurity camera system serves to ensure detection accuracy whileminimizing implementation costs, which is highly desirable.

Optical system 19 preferably includes an optical lens 25, which capturesvisible light in its field of view within the monitored environment, andan image sensor 27 that converts the visible light captured by lens 25into a corresponding digital video signal S_(V). As seen, image sensor27 is in electrical communication with ISP 23. As a result, digitalvideo signal S_(V) produced from optical system 19 is streamed to ISP 23for subsequent processing.

PIR detector circuit 21 preferably includes a Fresnel lens 29, whichrefracts all light in its field of view within the monitoredenvironment, a PIR sensor 31, which converts any infrared (IR) radiationfrom the refracted light into a corresponding voltage, and a signalconditioning circuit 33 that converts the voltage produced by PIR sensor31 into a corresponding digital IR radiation signal S_(IR). As can beseen, signal conditioning circuit 33 is in electrical communication withISP 23. As a result, digital IR radiation signal S_(IR) produced fromcircuit 33 is delivered to ISP 23 for processing.

As can be appreciated, signal conditioning circuit 33 preferablyincludes a microcontroller that is specifically tuned to monitor aparticular IR radiation range within the field of view (namely, thecorresponding thermal energy range which is indicative of the presenceof a person). Based on the voltage produced by PIR sensor 31, circuit 33produces a series of intermittent yes/no-type temperature signalsS_(IR), with a “yes” signal denoting that a trigger condition has beenmet (e.g., a thermal energy variance within the field of view which isindicative of the presence of a person) and a “no” signal denoting thata trigger condition has not been met.

Preferably, signal conditioning circuit 33 compares two sensor readings(e.g., by analyzing the outputs of a pair of separate PIR sensors 31) toobtain IR radiation differentials within the field of view. Using thistechnique, the average, or natural, temperature within the field of viewis effectively normalized. Among other things, this technique furtherenables circuit 33 to compensate for (ii) broader changes throughout theentire field of view that may be attributable to lighting and/ortemperature changes within the monitored environment and (ii)common-mode interference that may be attributable to nearby electricfields.

Although separate complementary pairs of lenses and sensors are used toproduce corresponding video and temperature signals, it is to beunderstood that the same lens and/or sensor could be used in conjunctionwith the production of both video signal S_(V) and IR radiation signalS_(IR). By eliminating such components, camera 13 may be effectivelyreduced in both size and cost of manufacture.

As referenced briefly above, image signal processor, or controller, 23is disposed in electronic communication with optical system 19 and PIRdetector circuit 21. Processor 23 is specifically programmed tocondition and mix digital video signal S_(V) and digital IR radiationsignal S_(IR) to yield combined analog signal S_(A). In turn, encodedanalog signal S_(A) is transmitted to video receiver 15 viacommunication channel 17 for subsequent decoding and analysis, whichwill be explained further below.

It should be noted that utilizing an analog signal format to transmitsignals from each camera 13 to receiver 15 provides system 11 with acouple notable advantages.

As a first advantage, because analog signal transmission protocols arerather limited in complexity, controller 23 requires minimal processingcapabilities. Consequently, a relatively inexpensive controller 23 couldbe utilized in each camera 13, thereby significantly reducing theoverall cost to manufacture system 11.

As a second advantage, analog signal transmission allows for the use ofanalog communication channels 17, which are often already configured incertain environments. As can be appreciated, analog communicationmediums, such as coaxial cables, are both generally inexpensive innature and can be relatively long in length without experiencing signaldegradation.

ISP 23 utilizes a novel method of conditioning and mixing digital videosignal S_(V) and digital IR radiation signal S_(IR) together to yieldcombined analog signal S_(A). As will be explained further in detailbelow, signal mixing is achieved by taking advantage of inherentconstructs of certain analog video transmission protocols.

Specifically, certain analog signal transmission protocols (e.g.,National Television System Committee (NTSC) and Phase Altering Line(PAL) transmission protocols) transmit video in a frame-by-frame manner.In the present invention, ISP 23 is able to combine streaming digitalvideo signal S_(V) with PIR sensor signal S_(IR) by inserting the IRradiation data in the space between successive frames of the videoduring conversion into analog form.

To illustrate the signal mixing concept set forth in detail above, asample signal waveform is shown in FIG. 2, the waveform being identifiedgenerally by reference numeral 111. As can be seen, sample waveform 111includes a first set, or frame, of active lines of video 113 and asecond set, or frame, of active lines of video 115 that are separated bya vertical blanking interval (VBI) 117. A limited portion of interval117 includes certain non-visible data used for video synchronization andequalization purposes. For instance, in waveform 111, a portion ofinterval 117 includes vertical synchronization pulses 119, which areused to indicate when the next successive frame of video is to commence,and color synchronization carriers 121.

As can be seen, PIR signal data, or component, 123 is embedded intowaveform 111 within interval 117. As previously referenced, PIR signalcomponent 123 is preferably of the yes/no variety, generating one ormore pulses of a first amplitude upon detecting a “yes” condition andone or more pulses of a second amplitude upon detecting a “no”condition. In this manner, video receiver 15 is easily able to discernwhen a IR radiation alert condition has occurred, as will be explainedfurther below.

Referring now to FIGS. 3(a) and 3(b), there are shown front perspectiveand side views, respectively, of one implementation of camera 13.However, it is to be understood that the implementation of camera 13shown in FIGS. 3(a) and 3(b) is provided for illustrative purposes onlyand that the overall design and configuration of camera 13 could bemodified without departing from the spirit of the present invention.

As represented herein, camera 13 comprises a common protective housing211 into which all the principal electronic components of camera 13 aredisposed in order to create a unitary item. Specifically, housing 211includes a generally cylindrical member, or canister, 213 that isappropriately dimensioned to retain optical system 19, detector circuit21 and signal processor 23.

A stem 215 extends orthogonally out from the rear of canister 213 and ispivotally coupled to a dome-shaped base 217, which is designed to befixedly mounted onto a wall or other similar surface. As such, theorientation of canister 213 can be adjusted, as needed, relative to base217 to modify the field of view for camera 13.

In the present embodiment, both optical system 19 and PR detectorcircuit 21 are shown retained within canister 213. To facilitateassembly of camera 13, canister 213 is designed with a narrow extension,or bump-out, 219 to receive PIR detector circuit 21 without interferingwith the larger components of camera 13.

Referring back to FIG. 1, video receiver 15 represents any devicecapable of receiving, analyzing and selectively recording video, such asa DVR or NVR. As can be seen, receiver 15 preferably includes a decoder35 for, inter alia, decoding analog signal S_(A) back into digital form,a main chipset, or microcontroller unit (MCU), 37 for, inter alia,determining when thermal-based and pixel-based motion detection exceedsa defined threshold, and a data storage device 39 for saving digitalvideo signal SD when MCU 37 determines a motion detection event.

Decoder 35 represents any device capable of receiving and decoding ananalog signal into digital form. As can be appreciated, decoder 35receives the analog video signal from each camera 13 and, in turn, isresponsible for both (i) decoding the video component of processedanalog signal S_(A) back into a corresponding digital video signal SDand (ii) generating a digital PIR flag signal Spa which indicates theyes/no status of the embedded PIR signal component in analog signalS_(A).

MCU 37 is in electrical communication with decoder 35 and is adapted toreceive both digital video signal SD and digital PIR flag signal Spa.Using the aforementioned digital signals, MCU engages in three principalprocesses, namely, (i) analyzing pixel changes in digital video signalSD to determine whether a pixel-based motion detection event hasoccurred, (ii) analyzing the status of digital PIR flag signal Spa todetermine whether a thermal-based motion detection event has occurred,and (iii) if both thermal-based and pixel-based motion detection isdetermined, initiating the predefined alert response (e.g. commencestoring of video signal SD into memory).

Preferably, pixel detection is achieved by programming MCU 37 to analyzeframes of digital video signal SD, wherein each video frame is an imagewhich contains a matrix of pixels. Because each pixel is assigned avalue which determines its color, a motion detection algorithm can beapplied by MCU 37 that compares the value of each pixel on aframe-by-frame basis to detect change. If pixel change is detected whichexceeds a predefined threshold (e.g., amongst a certain minimum-sizedpixel cluster), a pixel-based motion detection event is assessed.

Storage device 39 is electrically connected to MCU 37 and is adapted toreceive and store video signal SD into memory. Accordingly, storagedevice 39 represents any device capable of storing video, such as alocal hard disk drive (HDD). Although storage device 39 is representedherein as being an internal component of receiver 15, it is to beunderstood that storage device 39 could be remotely located (e.g., acloud-based data storage solution) without departing from the spirit ofthe present invention.

As referenced above, communication channel 17 represents anyconventional communication medium that is capable of transmitting ananalog signal. For instance, channel 17 may be in the form of a lengthof relatively inexpensive, analog coaxial cable that directly connectseach camera 13 to common receiver 15. Alternatively, channel 17 may bein the form of a wireless communication path, thereby facilitating theinstallation of cameras 13.

Operation of Security Camera System 11

Security camera system 11 is designed to operate in the followingmanner. As referenced above, each camera 13 is designed to compile acontinuous stream of digital video S_(V) for the monitored environment.Additionally, each camera 13 measures IR light within the monitoredenvironment, thereby allowing for the detection of any change in IRradiation within the environment that is indicative of relevantmovement, such as a change in thermal energy attributable to body heat.

Signal processor 23 then mixes digital video signal S_(V) and digital IRradiation signal S_(IR) together to yield a combined analog signalS_(A). As a feature of the invention, ISP 23 can process each of theaforementioned digital signals using different analog transmissionprotocols. Accordingly, it is to be understood that the principles ofthe present invention could be applied or retrofitted across a broadspectrum of digital and analog security camera systems, which is highlydesirable.

Mixed analog signal S_(A) from each camera 13 is then transmitted inanalog form to common receiver 15 via analog communication medium 15. Ascan be appreciated, the use of analog signal transmission technologysubstantially reduces the manufacturing cost associated with system 11,which is highly desirable.

Upon receipt of combined analog signal S_(A), receiver 15 decodes thevideo steam back into digital form and engages in an analysis todetermine whether both IR radiation-based and pixel-based motiondetection has occurred within the monitored environment. For ease inunderstanding how video receiver 15 engages in its motion detectionanalysis, a series of illustrative screen displays are shown in FIGS.4(a)-(c).

In FIG. 4(a), there is shown a sample screen display, or video frame,211 of a digital video stream SD compiled and analyzed by video receiver15. As can be seen, frame 211 of video stream SD is shown at a moment intime in which there is no motion detected within the monitoredenvironment, which is represented herein as an office.

By contrast, in FIG. 4(b), there is shown a second sample screendisplay, or video frame, 221 of a digital video stream SD compiled andanalyzed by video receiver 15. As can be seen, a plurality of cables 223has fallen into the field of view. Because receiver 15 monitors pixelchanges in the video feed, the pixel changes attributed to the movementof cables 223 triggers a pixel-based motion detection motion event. Upondetecting the pixel-based motion detection event, MCU marks video streamSD with a corresponding tag 225, represented herein simply as the letter“M.”

It should be noted that the presence of cables 223 does not similarlyinduce a thermal energy-based motion detection event because no notablechange in infrared radiation is detected within the field of view (e.g.,thermal energy falling within the typical range of human body heat).Because no relevant, thermal-based movement is detected within the fieldof view, the pixel-based detection event motion is consideredinconsequential (e.g., not a human intrusion) and, as such, no alertresponse is undertaken.

However, in FIG. 4(c), there is shown a third sample screen display, orvideo frame, 231 of a digital video stream SD compiled and analyzed byvideo receiver 15. As can be seen, a hand 233 is present within thefield of view. The thermal radiation produced from hand 233 is detectedby PIR detector circuit 21 and, in turn, yields an indicative digital PRsignal S_(IR). Receiver 15 ultimately identifies that a IRradiation-based motion detection event has occurred and marks videostream SD with a corresponding tag 235, represented herein simply as“PIR.”

Additionally, by monitoring pixel changes in the video feed, the initialmovement of hand 233 within the field of view triggers a pixel-basedmotion detection event. Upon detecting the pixel-based motion detectionevent, MCU marks video stream SD with a corresponding tag 237,represented herein simply as the letter “M.”

It should be noted that if both IR radiation-based and pixel-basedmotion detection events are detected, video receiver 15 engages in anappropriate alert response, such as commencing storage of the video feedSD into data storage device 39. However, it is to be understood that thetriggering of an alert response is only undertaken when both types ofevents are detected, thereby eliminating frequent false trigger eventsthat generally occur when only one of the two events is detected.

Features and Advantages of the Present Invention

As can be appreciated, the construction and operation of security camerasystem 11 yields a number of notable advantages over traditionalsecurity camera systems.

As a first advantage, security camera system 11 incorporates IRradiation-based motion detection capabilities into an analog-basedsecurity camera system. Due to certain inherent positive characteristicsassociated with analog-based signal transmission systems (e.g., lowercosts, longer signal transmission capabilities), a highly advantageoussecurity camera system can be achieved.

As a second advantage, security camera system 11 utilizes IRradiation-based and pixel-based motion detection, in tandem, to increasethe accuracy in sensing relevant movement, such as the presence of aperson within a monitored environment. In fact, testing indicates thatthe use of the two aforementioned motion detection techniques candiminish the occurrence of false trigger events by as much as 90%.

The embodiment shown above is intended to be merely exemplary and thoseskilled in the art shall be able to make numerous variations andmodifications to it without departing from the spirit of the presentinvention. All such variations and modifications are intended to bewithin the scope of the present invention as defined in the appendedclaims.

What is claimed is:
 1. A security camera system for monitoring adesignated area for relevant movement, the security system comprising:(a) a video transmitter, comprising, (i) an image capture device forproducing a streaming digital video signal of the designated area, (ii)a PIR detector circuit for measuring infrared radiation within thedesignated area, the PIR detector circuit producing a digital infraredradiation signal that indicates relevant movement within the designatedarea based on measured infrared radiation, and (iii) a signal processorfor processing the digital video and infrared radiation signals togetherto yield a mixed signal, the signal processor transmitting the mixedsignal; and (b) a video receiver adapted to receive and decode the mixedsignal transmitted from the video transmitter into a correspondingdecoded digital signal with multiple image frames, each image framecomprising a plurality of pixels, the video receiver detecting a numberof pixel changes between successive image frames in the decoded digitalsignal; (c) wherein the video receiver analyzes the decoded digitalsignal and triggers an alert condition only when both the amount ofmeasured infrared radiation and the number of detected pixel changes inthe decoded digital signal indicates relevant movement within thedesignated area.
 2. The security camera system of claim 1 wherein thevideo receiver compares the number of detected pixel changes betweensuccessive image frames in the decoded digital signal against apredefined threshold value.
 3. The security camera system of claim 2wherein PIR detector circuit comprises: (a) a lens for refracting lightwithin the designated area; (b) a PIR sensor for converting infraredradiation in the light refracted by the lens into a correspondingvoltage; and (c) a signal conditioning circuit for comparing the voltageproduced by the PIR sensor against a predefined voltage range, thesignal conditioning circuit generating a digital infrared radiationsignal indicative of an infrared radiation-based alert condition whenthe voltage produced by the PR sensor falls within the predefinedvoltage range.
 4. The security camera system of claim 3 wherein thevideo receiver triggers an alert condition only when both when thenumber of detected pixel changes exceeds the predefined threshold valueand the voltage produced by the PIR sensor falls within the predefinedvoltage range.
 5. The security camera system of claim 4 wherein thevideo receiver comprises: (a) a decoder for decoding the mixed signalinto a corresponding decoded digital signal that includes a digitalvideo signal component and a digital PIR flag signal component; and (b)a microcontroller unit for analyzing the digital PIR flag signalcomponent to determine the presence of the infrared radiation-basedalert condition, the microcontroller being programmed to compare thenumber of pixel changes between successive image frames in the decodeddigital signal against the predefined threshold value.
 6. The securitycamera system of claim 5 wherein, upon determining an alert condition,the microcontroller unit initiates a predefined alert response.
 7. Thesecurity camera system of claim 6 wherein the video receiver furthercomprises a data storage device.
 8. The security camera system of claim7 wherein, as the predefined alert response, the microcontroller unitstores the digital video signal component of the decoded digital signalin the data storage device.